Looks like the data leak is also affecting At&t and not just Verizon. Reports are saying its not the carrier but the iOS 6 update. A the moment Verizon has fixed the issue and At&t is currently working on the issue.

An update was delivered yesterday to Verizon iPhone 5 owners experiencing an issue where cellular data would be used even when the device is connected to Wi-Fi. The carrier confirmed to 9to5Mac in a statement that customers will not be charged for the data, but it looks like the issue is not Verizon-only. We received multiple reports of the same issue from AT&T customers, indicating the problem might be related to iPhone 5/iOS 6 rather than Verizon-specific.